A conventional belt buckle device generally includes a frame which has a tongue extending from one of two ends of the frame so that the belt extends through the frame and the tongue is engaged with one of the apertures in the belt. However, the periphery defining the aperture which is often used to engage with the tongue will be deformed, elongated or even broken, and the deformed aperture can be seen when wearing the belt. Another belt buckle device includes a board-type member which has a tongue extending from the rear side of the board-type member, the belt passes by the rear side of the board-type member so that the tongue may extends through one of the apertures in the belt. When operating either one of the two conventional belt buckle devices, the frame or the board-type member has to be pulled outwardly so that the tongue can be disengaged from the aperture of the belt.
The present invention intends to provide a belt buckle device which has a rotatable member with a protrusion which is engaged with or disengaged from the belt by simply pushing a button on the frame.